Having just checked an old Chimp Studbook, I now know that chimps were kept at Howletts until 1982, before being transferred to Port Lympne. As Pertinax has commented in the companion photo to this one, the chimps used the brick dens in the corner of the cage and the roof of these dens was wired off from the rest of the enclosure for their use during the day, which made them quite hard to see. This roof is just visible on the left of this photo, but the wires are not, although I presume that the chimps would have been there when I took this photo. I have seen videos of chimps using the large area too, but this must have been infrequent as the gorillas had it most of the time.
